Method and apparatus for the transfer of fluid samples

ABSTRACT

A fluid sample is transferred to a gellike substance by first suspending the sample in slits of an applicator that retain the sample by capillary action. The slits extend transversely through the applicator and intersect a wedge shaped end of the applicator. The insertion of the applicator in the gel forms an incision therein and the wedge shaped end opens the incision so that the gel contacts the sample in the slit. Forces acting on the suspended sample cause the transfer of at least a portion thereof to the gel. Upon withdrawal of the applicator the same portion is retained in the gel. Apparatus for performing the above described steps comprising a bridge applicator and means for holding a fluid sample and the gel is also disclosed.

United States Patent [72] inventors Christopher J. Sicbert Berkeley; Douglas W. l-iull, Richmond, both of Calif. [2 1] Appl. No. 876,456 [22] Filed Nov. 13, 1969 [45] Patented Oct. 26, 1971 [73] Assignee Bio-Rad Laboratories Richmond, Calif.

[54] METHOD AND APPARATUS FOR THE TRANSFER OF FLUID SAMPLES 19 Claims, 7 Drawing Figs. [52] US. Cl 204/180 G, 204/299 [51] Int.(l 801k 5/00 [50] Field of Search 204/299, 180 G, 180 R; 23/259 [56] References Cited UNITED STATES PATENTS 2,868,020 l/l959 Williams 23/259 3,317,418 5/1967 Zec 204/299 3,360,454 12/1967 Sahmel... 204/299 3,428,547 2/l969 Zec 204/299 3,499,360 3/1970 Davis 83/451 Primary Examiner-John H. Mack Assistant Examiner-A. C. Prescott Anorney-Townsend and Townsend ABSTRACT: A fluid sample is transferred to a gellike substance by first suspending the sample in slits of an applicator that retain the sample by capillary action. The slits extend transversely through the applicator and intersect a wedge shaped end of the applicator. The insertion of the applicator in the gel forms an incision therein and the wedge shaped end opens the incision so that the gel contacts the sample in the slit. Forces acting on the suspended sample cause the transfer of at least a portion thereof to the gel. Upon withdrawal of the applicator the same portion is retained in the gel. Apparatus for performing the above described steps comprising a bridge applicator and means for holding a fluid sample and the gel is also disclosed.

PATENTEUUCT 26 I97! 3, 6 1 6 387 INVIZNTORS CHRISTOPHER J. SIEBERT BY DOUGLAS W. HULL mm; Li W ATTORNEYS METHOD AND APPARATUS FOR THE TRANSFER OF FLUID SAMPLES BACKGROUND OF THE INVENTION During testing and particularly during clinical testing such as gel electrophoresis, it has heretofore been common practice to place a fluid sample, such as blood serum, into a gellike substance, such as agarose gel, in accordance with various manual techniques. The sample migrates into the gel and an electric current is passed through the gel and the sample which causes a separation of the sample components. Blood serum samples separate into four main classes of Iipoproteins, namely chylomicrons, beta, prebeta, and alpha, although other substances such as cholesterol, triglycerides, and phospholipids are associated in varying ratios with each such class. Each lipoprotein migrates into the gel a different distance to define bands that are spaced according to the mobility of the particular lipoprotein during electrophoresis. The bands are then analyzed, either in a spectrometer or visually by conventionally staining the gel. The analysis provides important clues about the patients cholesterol condition, provides clues as to his susceptibility to heart attacks or other coronary conditions and is thus a valuable tool in the medical examination of patients.

Since tests of the above-described character are comparative tests it is of great importance to provide identical test conditions so as to eliminate operator errors, inconsistencies and the like from influencing the test results. The transfer of the sample to the gel is a source of major deviations in the test conditions and, therefore, the test results.

Prior art test procedures rely almost exclusively on the technicians skill and particularly on the technician's skill of reproducing the quantitative and qualitative transfer of the sample into the gel. Identical results are almost impossible to obtain so that the test results have a limited accuracy and reliability. This in turn requires that a significant error margin must be taken into consideration so that minor variations in the composition of the sample cannot be detected. Prior art methods and apparatus are therefore limited to detecting only major changes in the sample.

Detailed descriptions of prior art sample transfer methods of the above described character, including summaries of their shortcomings in terms of repeatability of the procedures, are contained in Cawley, Electrophoresis and Immunoelectrophoresis, pages 227 through 235, published by Churchill & Company, London, 1969; and Wieme, Agar Gel Electrophoresis, Elsevier Publishing Company, Amsterdam, 1965, pages 61 through 77. A review of these and other references illustrates the problems caused by uncontrolled and, therefore, nonrepeatable sample transfer techniques and conditions. In addition, prior art techniques are relatively cumbersome, time consuming and, therefore, costly.

SUMMARY OF THE INVENTION The present invention provides a method and apparatus for the uniform and controlled transfer of fluid samples into a gellike substance to thereby enable the repetition of the transfer under substantially identical conditions. Quantitative and qualitative analysis of the sample thus yields tests results which are a function of the prevailing sample conditions rather than an undeterminable mixture of changes in the sample and unpredictable variations caused by nonuniform transfer techniques.

In its broadest aspects the present invention comprises the steps of: suspending the sample in a cavity by capillary forces between the sample and material, the material defining at least one opening communicating with the exterior in a plurality of directions, and forming a groove in the substance. The cavity is placed in the groove to establish contact between the substance and the sample. The cavity is withdrawn from the groove in a direction so that the opening defines the trailing end of the cavity whereby a quantity of the sample is withdrawn from the cavity and retained in the substance.

The term groove" as used herein means a volume from which the substance has been displaced irrespective of the shape or permanence of such displacement.

The apparatus of the present invention provides a bridge shaped applicator guided in a pair of spaced apart, up-right guide posts which project from a support structure or base. A tongue terminating in a wedge shaped end including a ridge and defining a sample suspending capillary cavity or slit that intersects the ridge projects from the application bridge towards the support structure. The tongue includes means communicating the cavity with the exterior at a point spaced from the ridge. The slit itself is dimensioned to control the quantity of the sample that is transferred to the substance. Means are also provided for alternatively positioning container means for the sample and means holding the substance beneath the applicator tongue.

The actual sample transfer from the container means to the holding means is performed by depressing the applicator bridge to insert the tongue in the container means, whereby capillary action fills the slit in the tongue with the sample, placing the substance holding means below the tongue, and moving the applicator bridge towards the holding means until the wedge shaped tongue portion enters the substance. The applicator bridge is then withdrawn from the substance and a quantity of the sample remains in the substance.

In contrast to prior art methods and apparatus for the transfer for fluid samples to deformable substances such as gels, the method and apparatus of the present invention enable a speedy transfer under substantially identical conditions. Fluctuations in the test results caused by technician errors, deviations from established procedures in performing prior art techniques and the like are eliminated so that any difference in the test results reflect actual variations in the test samples. This imparts reliability to the test results. In addition, it enables the detection of much lesser degrees of sample variations since deviations introduced during the sample transfer have been removed and need no longer be taken in account.

In the preferred embodiment of the invention the applicator includes a plurality of independent, spaced-apart capillary cavities which are simultaneously inserted in the gel and deposit the sample in an elongated groove. The slit-shaped cavities extend above the upper surface of the gel and permit the formation of gel portions between and interconnecting the opposing sides of the groove. These gel portions help maintain a uniform electrical field across the width of the gel (and the length of the groove) during subsequent electroplierosis.

The scientific principles which underlie the fluid transfer from the capillary cavities to the incision in the gel are presently not precisely understood or known. The following description of what is believed to cause the superior sample transfer provided by the present invention are offered by way of explanation only and not to limit the invention to any particular scientific principle.

It is believed that as soon as an initial contact between the wedge shaped end of the applicator and the gel is obtained, capillary forces are created between the gel and the suspended sample which tend to withdraw at least a portion of the sample from the slits in the applicator. As the wedge shaped end is forced. into the gel the slits permit narrow, web shaped portions of gel to remain between opposing walls of the gel defining the incision. These webs enter the capillary cavities and thus displace a portion of the sample from the slits. Capillary forces between the gel and the sample continue to act and, upon withdrawal of the applicator from the gel, an additional quantity of the sample appears to be withdrawn.

The transverse extend of the slits over the full width of the applicator also appears to substantially enhance the sample flow from the capillary cavity to the gel even if gel entered the capillary cavities during the initial insertion of the applicator in the gel. Upon withdrawal of the applicator, transfer of the sample from the capillary cavity to the gel might be further enhanced by the presence of small empty spaces immediately adjacent the ridge and the wedge shaped end of the applicator.

This space might provide additional room for a sample being withdrawn from the capillary cavities. In addition, it is possible that the empty space is under vacuum so that a pressure differential between the exterior atmosphere and the empty space acts on the fluid sample in the capillary cavity (which communicates with both) and thus forces an additional quantity of the sample into the gel.

The extent to which the above enumerated phenomena determine the sample transfer is not known and it is not certain that each one of the phenomena is present and effective in the described manner. Their combined efficiency in transferring relatively large quantities of sample, as compared to prior transfer methods, in very short time periods, usually no longer than the time it takes to depress and release the applicator, illustrate the effectiveness of the invention and the improvement it affords over the prior art.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a perspective side elevational view of a fluid sample transfer apparatus constructed in accordance with the present invention;

FIG. 2 is a fragmentary side elevational view of the transfer apparatus and illustrates the transfer of the sample from a sample container to the applicator;

FIG. 3 is a view similar to FIG. 1 but illustrates the transfer of a quantity of the sample from the applicator to a tray holding the gel;

FIG. 4 is an enlarged, fragmentary plan view of the guide means for the applicator;

FIG. 5 is an enlarged, fragmentary plan view of an end portion of the gel holding tray;

FIG. 6 is an enlarged, fragmentary elevational view of a portion of an applicator constructed in accordance with the present invention; and

FIG. 7 is a side elevational view of the applicator portion illustrated in FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 through 5, a fluid sample transfer apparatus l constructed in accordance with the invention principally comprises a base or support structure 12, guide means 14 projecting from the base, and an applicator l6 movable along the guide means to and from the base, container means I8 for holding a fluid sample and a tray or slide 20 holding the gel (not shown in FIGS. I through to which the sample must be transferred are also provided.

Container means 18 has a generally rectangular configuration and includes a plurality of equally spaced, side-by-side, cup shaped depressions 22 which are identified with letters A, B and C.

Slide is relatively long and includes three adjacent, equally spaced and parallel troughs 24 which extend substantially over the full length of the slide. One end of the slide includes identification letters A, B, C, for each trough. The spacing between and the width of the troughs substantially equal the spacing between and width of depressions 22 of the container means.

Base 12 is constructed of a pair of spaced-apart guide plates 26, 27 which are suitably secured to the face of a base plate 28 and which define contiguous first and second tracks 30 and 32 for slideable movement of the container means and the tray, respectively, under applicator I6. First track 30 has a width about equal to the width of container means 18 and extends from one end of the base past applicator l6 and terminates at t a shoulder 34 defined by guide plates. The distance: between shoulders 34 and the vertical projection of applicator 12 is about equal to the spacing between forward edge 36 of the container means and the center of the cup-shaped depressions 22. Slideable movement of the container means into engagement with shoulders 34 thus aligns the cup-shaped depressions with the applicator. Guide plates 26, 27 further include projections 38 which limit the movement of the container means beyond first track 30 and base 12.

Second track 32 defined by guide plates 26, 27 has a width substantially equal to the width of tray 20 to permit insertion and slideable movement of the tray therein. It will be noted that the free end of track 32 does not include movement limiting projections as does the free end of track 30 so that the slide can extend past the end of base 12 and track 32. Movement of the slide in track 32 towards container means I8 is, however, limited by the engagement of the slide, the container means and projections 38 of the guide plates as illustrated in FIG. 3. When these three members are in mutual abutment the distance between the projection of applicator l6 and the end of the tray in contact with the container means is always the same for advantages pointed out hereinafter.

Referring to FIGS. 1 through 4, applicator 16 comprises a relatively thin, flat and substantially rectangular shaped applicator bridge 40, which, at its outer, vertical sides, includes a pair of generally cylindrical, elongate guide bars 42. The up plicator further includes a plurality of equally spaced, side-byside applicator tongues 44 which project from the lower horizontal bridge edge towards base 12 and a substantially horizontal, flat contact bar 46 at its upper horizontal edge. The spacing between tongues 44 equals the spacing between cup-shaped depressions 22 of container means 18 and troughs 24 of tray 20 and they are also identified with letters A, B and C to correspond with the letters of the container means and the tray. The width of the tongues, however, is less than the width of the corresponding depressions and troughs.

Guide means 14 comprise a pair of spaced apart, longitudinally slitted tubular posts 48 which project on each side of track 30 from base 12. The cylindrical applicator guide bars are disposed in the cylindrical interior of the posts and applicator bridge 40 extends through the slits and the posts so that the applicator can be moved to and from base l2 along the guide posts. Helical compression springs 50 are placed in the interior of the guide posts between the base and the lower end of the cylindrical applicator bars 42. Unless the applicator is depressed against the spring force the springs position the applicator above base 12 to permit movement of container means 18 and tray 20 beneath the tongues 44.

Referring now to FIGS. 6 and 7, each applicator tongue 44 is flat and constructed of a relatively thin sheet. The tongue terminates in a wedged shaped lower end 52 defined by a substantially sharp ridge 54 and a pair of angularly inclined surfaces 56 which converge from faces 58 of the tongue to the ridge. The tongue and the applicator bridge are preferably of a one-piece construction.

A plurality of slits or capillary cavities 60 extend from ridge 54 towards a central portion 62 of the tongue. The slits intersect at least one face 58 and preferably they extend across the full thickness of the tongue (as best seen in FIG. 7). The slits are defined by inner cavities 64 ending in contiguous passageways 66 that terminate in necks 68 that form the narrowest portion of each slit. Thus, there is fluid communication between the capillary cavities and the exterior in a plurality of transverse directions.

The transition between the inner cavities and the tapered passageways is spaced from ridge 54 of the tongue a distance substantially equal to the distance between the ridge and the projected intersection between tongue faces 58 and inclined surfaces 56.

The width W of slits 60 is sufficiently small so that fluid disposed within the slit is retained therein by capillary action between the fluid and the tongue walls defining the slit. Thus, maximum dimensions for W will vary to some extent with the composition of the fluid and the material of which the tongue is constructed.

As more fully described hereinafter, in a particularly frequent application of this invention the fluid sample retained in slits 60 is blood serum while the applicator l6 and tongue 44 are constructed of the molded plastic material. For such an application it has been determined that width W of the slits should be between about 0.012 and about 0.024 inch and preferably is about 0.018 inch. Furthermore, for purposes more fully described below, the width of the slits at necks 68 of passageways 66 is between about one-half to about onefourth the slit width W and, preferably, about one-third that width. For the above stated application of the invention the width of neck 68 is preferably about 0.006 inch.

The dimensioning of slits 60 is relatively critical. They may be machined in accordance with well-known methods or molded by special techniques capable of achieving the necessary dimensions.

Turning now to the operation of sample transfer apparatus and referring to the drawings, a relatively thin gel layer of between one-fourth to about uniform gel layer thicknesses and application techniques, and to reduce application costs since mass production techniques can be applied. Fluid samples, say 3 different blood serum samples identified with letters A, B and C are poured into the cup shaped depressions 22 of container means 18 and the container means is moved along tracks 30 until it engages shoulders 34 of guide plates 26, 27. Applicator 16 is now manually depressed whereby the lower, wedge shaped ends 52 of applicator tongues 44 enter the cup shaped depressions and contact the serum samples therein. Capillary forces draw the sample into capillary cavities 60 in tongues 44 until the cavities are filled. Upon release of the applicator compression springs 50 bias it upward away from container means 18 and the latter are moved along tracks 30 until in engagement with guide plate projections 38.

relative position of the sample deposited in the gel is also the same so that when the electric current is applied to the gel the sample is always at the same relative position. Variations in the test results from differences in the sample position are thereby eliminated.

Applicator 16 is again depressed whereby ridge 54 enters the gel. To prevent the uncontrolled pushing, squeezing or compression of gel beneath the ridge the latter is defined by a sharp edge (unlike shown in FIG. 7, which is a grossly exaggerated illustration of the ridge) that has a maximum flat width of no more than 0.010 inch and preferably a width of about 0.0075 inch. With such a ridge the lower wedge shaped end of the applicator tongues form an incision in the gel and, as the lower tongue ends penetrate the gel, they cut therethrough. The converging surfaces 56 of the tongue bias 72 of the gel to ridge 54 ofthe tongue. The groove defining gel walls now rest against the converging surfaces 56 of the tongue and contact the serum sample disposed in slits 60.

Upon release of the applicator springs 50 bias it upward away from slide 20 so that the wedge-shaped tongue end 52 is withdrawn from groove 70. Upon withdrawal the groove walls follow the wedge-shaped tongue end and gradually close the groove. The rate of sample transfer is a function of the size and shape of neck 66. By properly dimensioning the neck only the desired quantity of serum is deposited in the groove. By varying the configuration and size of the passageway and the neck the quantity of serum deposited in the groove can be adjusted.

Springs 50 keep the withdrawal force and speed constant so that all sample transfer parameters are controlled and the quantity of sample deposited during each transfer is virtually identical. As already mentioned, subsequent test results thereby become much more reliable and free of subjective variations and consequent inaccuracies.

It has been found that best gel cutting action of the lower wedge shaped tongue end 52, optimal groove configurations and best repeatability of the test results is obtained when the inclined surfaces 56 converge at an angle between about and about 60. For the deposit of blood serum in agarose gel that angle is preferably about 30 to 45. This wedge configuration assures at least partial closing of the groove which aids in the uniformity of the electric field during the subsequent electropherosis in the sample area.

The configuration of tongues 44, and particularly the intersection of ridge 54 by capillary cavities 60 results in the formation of a groove that includes web like quantities of gel (not separately shown) between opposing sides of the groove and which are spaced apart a distance equal to the spacing of the capillary cavities.

Upon initial contact between the gel and the tongues, through the insertion of the tongues, and until withdrawal of the tongues from the gel, at least a portion of the samples suspended in the capillary cavities is transferred to the gel in the above described manner. For the desired, high-speed transfer of an appreciable quantity of the sample it is necessary to withdraw the applicator in a direction opposite to a direction in which the capillary cavities communicate with the exterior so that an open end of the slit (as at neck 68) defines the trailing end of the cavity during its withdrawal. If the applicator were constructed and withdrawn so that this condition is not met, the sample transfer would be unsatisfactory. Accordingly, applicator 16 is withdrawn upwardly, parallel to its vertical sides and away from ridge 54 as can be seen by a comparison of FIGS. 3 and l (applicator released). During subsequent tests the webs aid in maintaining a uniform electrical field in the sample area of the gel. The webs also strengthen the gel in the area of the groove. Furthermore, and as already referred to, the webs appear to aid in the sample transfer to the gel.

The components of the transfer apparatus of the present invention are simple and can be inexpensively mass produced. Consequently components that contact the sample can be disposed of to facilitate the speed with which tests are performed, reduce laboratory work and, thus, laboratory costs. In addition possible contamination of the sample with remnant of previous samples on the components, and consequent distortion of the test results, is thereby eliminated. Furthermore, the number of applicator tongues 44, slide troughs 24 and cup shaped depressions 22 in container means 18 can be altered to suit particular requirements and application.

In the preferred embodiment of the invention the applicator includes a plurality of independent, spaced apart capillary cavities which are simultaneously inserted in the gel and deposit the sample in an elongated groove. The slit-shaped cavities extend the upper surface of the gel and permit the formation of gel portions between and interconnecting the opposing sides of the groove. These gel portions help maintain a uniform electrical field across the width of the gel (and the length of the groove) during subsequent electropherosis.

The scientific principles which underlie the fluid transfer from the capillary cavities to the incision in the gel are presently not precisely understood or known. The following description of what is believed to cause the superior sample transfer provided by the present invention are offered by way of explanation only and not to limit the invention to any particular scientific principle.

it is believed that as soon as an initial contact between the wedge shaped end of the applicator and the gel is obtained, capillary forces are created between the gel and the suspended sample which tend to withdraw at least a portion of the sample from the slits in the applicator. As the wedge shaped end is forced into the gel the slits permit narrow, web shaped portions of gel to remain between opposing walls of the gel defining the incision. These webs enter the capillary cavities and thus displace a portion of the sample from the slits. Capillary forces between the gel and the sample continue to act and, upon withdrawal of the applicator from the gel, an additional quantity of the sample appears to be withdrawn.

The transverse extent of the slits over the full width of the applicator also appears to substantially enhance the sample flow from the capillary cavity to the gel even if gel entered the capillary cavities during the initial insertion of the applicator in the gel. Upon the withdrawal of the applicator, transfer of the sample from the capillary cavity to the gel might be further enhanced by the presence of small empty spaces immediately adjacent the ridge and the wedge shaped end of the applicator. This space might provide additional room for a sample being withdrawn from the capillary cavities. In addition, it is possible that the empty space is under vacuum so that a pressure differential between the exterior atmosphere and the empty space acts on the fluid sample in the capillary cavity (which communicates with both) and thus forces an additional quantity of the sample into the gel.

The extent to which the above enumerated phenomena determine the sample transfer is not known and it is not certain that each of the phenomenon is present and effective in the described manner. Their combined efficiency in transferring relatively large quantities of sample, as compared to prior transfer methods, in very short time periods, usually no longer than the time it takes to depress and release the applicator, illustrate the efi'ectiveness of the invention and the improvement it affords over the prior art.

We claim:

1. A method of placing a fluid sample into a substance comprising the steps of: suspending the sample in a cavity by capillary forces. between the sample and material defining the cavity, the material defining at least two angularly inclined exterior surfaces and at least one opening communicating the cavity with the exterior surfaces forming a groove in the substance, placing the cavity in the groove to establish contact between the substance and the sample, and withdrawing the cavity from the groove in a direction so that at least a portion of the opening defines the trailing end of the cavity whereby a quantity of the sample is withdrawn from the cavity and retained in the substance.

2. A method according to claim 1 wherein the step of forming the groove includes making an incision in the substance and forcing the substance on each side of the incision in opposing directions to open a groove having dimensions creating capillary forces between the substances and the sample suspended in the cavity.

3. A method in accordance with claim 1 including the step of forcing substance into the cavity through a portion of the opening to thereby displace a portion of the sample from the cavity.

4. A method in accordance with claim 1 including the step of positively guiding the cavity along a motion restricting path to and from the substance to thereby increase the reproducibility of the sample deposition in the groove.

5. in the method of performing electrophoresis tests of a fluid sample by placing the sample in a gellil e material, migrating the sample into the material, and applying an electric current to the material and the sample, the improvement comprising the steps of: transferring the sample to the material by suspending a portion of the sample in an elongate capillary cavity of an applicator having a cutting edge intersected by the cavity, the applicator including means communicating the cavity with the exterior over at least a portion of the length of the cavity, moving the applicator towards the material in the general direction of an axis of the cavity to contact the material with the cutting edge and form a groove in the material, contacting the suspended sample in the cavity with a portion of the material defining the groove, and withdrawing the applicator from the material in the general direction of the cavity axis, whereby at least a portion of the suspended sample is removed from the cavity and transferred to the material.

6. A method according to claim 5 including the steps of mounting the applicator on guide means, placing the sample container beneath the applicator, dipping the applicator in the sample container by moving it along the guide means, placing the material beneath the applicator, and moving the applicator along the guide means to contact the suspended sample with the material defining the groove.

7. A method according to claim 5 wherein the applicator has a wedge shaped end, and wherein the step of forming the groove comprises making an incision and forcing apart portions of the material adjacent the incision, and entering a portion of the material into the cavity to displace at least a portion of the suspended sample from the cavity.

8. Apparatus for depositing a fluid sample in a deformable substance comprising: an applicator member defining at least one cavity extending from an edge of the member towards an inner portion thereof and transversely across the member to intersect at least one side of the member, the cavity being dimensioned so that the sample can be retained therein by capillary forces, the edge of the member to which the cavity extends being defined by converging sides and a relatively sharp ridge between the sides intersected by the cavity.

9. Apparatus according to claim 8 wherein the member is defined by a sheet, wherein the sharp ridge is disposed at about the center of the sheet cross section, and wherein the converging sides comprise a pair of angularly disposed sides converging from faces of the sheet towards the ridge.

10. Apparatus according to claim 8 wherein the cavity is defined by a passageway extending from the ridge towards the inner portion of the member, and an inner cavity portion communicating with the passageway, the cavity portion having a width greater than a width of the passageway.

11. Apparatus according to claim 10 wherein the width of the cavity portion is from between about 2 to about 4 times the minimum width of the passageway.

12. Apparatus according to claim 11 wherein the passageway tapers from the cavity portion towards the ridge and there defines a neck, and wherein the neck has a width of between about 0.003 to about 0.0 l 0 inches.

13. Apparatus according to claim 8 wherein the applicator includes a plurality of equally spaced cavities, wherein the ridge has a maximum flat extent of no more than about 0.0l0 inch, and wherein the angular inclination of the converging sides is between about 15 and about 60.

14. Apparatus for the transfer of a fluid sample to a gel-like substance under controlled and repeatable conditions comprising: an applicator, guide means mounted to a support structure permitting movement of the applicator to and from the support structure, container means for the sample, means for holding the substance, and means for alternatively placing the container means and the substance holding means beneath the applicator, the applicator defining a tongue extending towards the support means, terminating in a wedge shaped end portion and having at least one capillary cavity intersecting the end portion, the tongue including means communicating the cavity with the exterior at a point spaced from the ridge, whereby depression of the applicator while the container means is beneath thereof transfers a portion of the sample into the cavity and depression of the applicator while the substance holding means is disposed beneath thereof causes the formation of an incision in the substance and the transfer of a quantity of the sample from the cavity to the incision.

15. Apparatus according to claim 14 wherein the tongue includes a plurality of independent, spaced apart capillary cavities.

16. Apparatus according to claim 14 wherein the alternative positioning means includes means for placing the substance holding means in a predetermined position beneath the applicator.

17. Apparatus according to claim 14 including spring means biasing the applicator away from the support structure.

18. Apparatus according to claim 14 wherein the applicator comprises a bridge member, and the guide means comprises a pair of spaced apart guide posts projecting from the support structure and moveably engaging the bridge member.

19. Apparatus according to claim 14 including a plurality of spaced apart applicator tongues projecting from a main body of the applicator, wherein the container means comprises a plurality of separated, equally spaced cups, and wherein the substance holding means comprises a plurality of equally 

2. A method according to claim 1 wherein the step of forming the groove includes making an incision in the substance and forcing the substance on each side of the incision in opposing directions to open a groove having dimensions creating capillary forces between the substances and the sample suspended in the cavity.
 3. A method in accordance with claim 1 including the step of forcing substance into the cavity through a portion of the opening to thereby displace a portion of the sample from the cavity.
 4. A method in accordance with claim 1 including the step of positively guiding the cavity along a motion restricting path to and from the substance to thereby increase the reproducibility of the sample deposition in the groove.
 5. In the method of performing electrophoresis tests of a fluid sample by placing the sample in a gellike material, migrating the sample into the material, and applying an electric current to the material and the sample, the improvement comprising the steps of: transferring the sample to the material by suspending a portion of the sample in an elongate capillary cavity of an applicator having a cutting edge intersected by the cavity, the applicator including means communicating the cavity with the exterior over at least a portion of the length of the cavity, moving the applicator towards the material in the general direction of an axis of the cavity to contact the material with the cutting edge and form a groove in the material, contacting the suspended sample in the cavity with a portion of the material defining the groove, and withdrawing the applicator from the material in the general direction of the cavity axis, whereby at least a portion of the suspended sample is removed from the cavity and transferred to the material.
 6. A method according to claim 5 including the steps of mounting the applicator on guide means, placing the sample container beneath the applicator, dipping the applicator in the sample container by moving it along the guide means, placing the material beneath the applicator, and moving the applicator along the guide means to contact the suspended sample with the material defining the groove.
 7. A method according to claim 5 wherein the applicator has a wedge shaped end, and wherein the step of forming the groove comprises making an incision and forcing apart portions of the material adjacent the incision, and entering a portion of the material into the cavity to displace at least a portion of the suspended sample from the cavity.
 8. Apparatus for depositing a fluid sample in a deformable substance comprising: an applicator member defining at least one cavity extending from an edge of the member towards an inner portion thereof and transversely across the member to intersect at least one side of the member, the cavity being dimensioned so that the sample can be retained therein by capillary forces, the edge of the member to which the cavity extends being defined by converging sides and a relatively sharp ridge between the sides intersected by the cavity.
 9. Apparatus according to claim 8 wherein the member is defined by a sheet, wherein the sharp ridge is disposed at about the center of the sheet cross section, and wherein the converging sides comprise a pair of angularly disposed sides converging from faces of the sheet towards the ridge.
 10. Apparatus according to claim 8 wherein the cavity is defined by a passageway extending from the ridge towards thE inner portion of the member, and an inner cavity portion communicating with the passageway, the cavity portion having a width greater than a width of the passageway.
 11. Apparatus according to claim 10 wherein the width of the cavity portion is from between about 2 to about 4 times the minimum width of the passageway.
 12. Apparatus according to claim 11 wherein the passageway tapers from the cavity portion towards the ridge and there defines a neck, and wherein the neck has a width of between about 0.003 to about 0.010 inches.
 13. Apparatus according to claim 8 wherein the applicator includes a plurality of equally spaced cavities, wherein the ridge has a maximum flat extent of no more than about 0.010 inch, and wherein the angular inclination of the converging sides is between about 15 and about 60*.
 14. Apparatus for the transfer of a fluid sample to a gel-like substance under controlled and repeatable conditions comprising: an applicator, guide means mounted to a support structure permitting movement of the applicator to and from the support structure, container means for the sample, means for holding the substance, and means for alternatively placing the container means and the substance holding means beneath the applicator, the applicator defining a tongue extending towards the support means, terminating in a wedge shaped end portion and having at least one capillary cavity intersecting the end portion, the tongue including means communicating the cavity with the exterior at a point spaced from the ridge, whereby depression of the applicator while the container means is beneath thereof transfers a portion of the sample into the cavity and depression of the applicator while the substance holding means is disposed beneath thereof causes the formation of an incision in the substance and the transfer of a quantity of the sample from the cavity to the incision.
 15. Apparatus according to claim 14 wherein the tongue includes a plurality of independent, spaced apart capillary cavities.
 16. Apparatus according to claim 14 wherein the alternative positioning means include means for placing the substance holding means in a predetermined position beneath the applicator.
 17. Apparatus according to claim 14 including spring means biasing the applicator away from the support structure.
 18. Apparatus according to claim 14 wherein the applicator comprises a bridge member, and the guide means comprises a pair of spaced apart guide posts projecting from the support structure and moveably engaging the bridge member.
 19. Apparatus according to claim 14 including a plurality of spaced apart applicator tongues projecting from a main body of the applicator, wherein the container means comprises a plurality of separated, equally spaced cups, and wherein the substance holding means comprises a plurality of equally spaced, separated substance holding troughs, the spacing of the tongues, the cups and the troughs being equal, and wherein the locating means positions the cups and the troughs beneath the applicator in alignment with the applicator tongues to enable the simultaneous transfer of a plurality of independent samples. 